This invention relates to a programmable timer, and more particularly to a programmable timer which may be set to control, automatically, the operation of electrical devices a plurality of times during a twenty-four hour time interval.
It is desirable to be able to control the operation of electrical devices through the use of a timer which automatically switches the devices on and off at desired times. This is particularly important to home owners, who, when absent from their homes, desire that lights, radios or other appliances be turned on and off to simulate normal activities of the household. There are many other uses for such timers.
It is particularly desirable that the devices can be switched on and off more than once in a twenty-four hour period by the timer, and that the timer be easy to read and to set, i.e. that there be no confusion as to the time the device is to be turned on and off. It is further desirable that the transition between on and off be accomplished by a snap action switch means so that no chattering or arcing between the switch contacts occurs.
Prior art timers have been unable to achieve all of these desirable features in a low cost unit. One common prior art timer has a rotating dial with hour indicating indicia thereon. A stationary pointer indicates the time as the hour indicia pass thereby. Two levers are provided, one of the levers setting an on time and the other lever setting an off time. Thus, each time the dial rotates it turns the device controlled by the timer on and off once. This is disadvantageous, and a further disadvantage is that the rotating dial is difficult to read and to use in properly setting the on and off times at the desired time of day.
Other prior art timers are somewhat similar in structure, i.e. incorporating a rotating dial, but have additional pins or levers for setting more than one on/off cycle in a given twenty-four hour period. In one instance, the pins are removable from the rotating dial and stored separately from the dial unless in use for setting an on or off time.
One other pertinent prior art timer included a clock having a clock face, which is surrounded by a plurality of discreetly mounted push/pull pins. A lever rotating with the hour hand of the clock, but below it, contacted the pins and caused electrical contacts to close for turning a device on at the indicated time. The contacts were opened when the lever moved passed a pin set to on, and the lever further included a cam for automatically returning the pin to its off position. This mechanism was quite complex and costly to manufacture, and was used primarily in laboratories rather than in the homes, and is no longer being produced.
Therefore, there still exists a need for a low cost programmable timer which is easy to read and to set, and which will switch devices attached thereto between their on and off conditions a plurality of times, as selected, in a given twenty-four hour period, wherein the switching is accomplished in a positive snap action manner.